Bovine respiratory syncytial virus.

Since the first report of BRSV in the 1970s, the understanding of this agent and its respective disease has increased dramatically. Current evidence supports a major role for this virus in bovine respiratory disease. Advances in diagnostics have increased the ability to demonstrate this virus in field outbreaks of respiratory disease. The clinical signs and pathologic features have been well described, and vaccines are available to aid in prevention and control. Still, many questions remain to be answered with respect to BRSV. It appears there may be antigenic subgroups of BRSV, but the epidemiologic significance and relevance to immunization of this remains unknown. The question of differences in virulence among isolates of this virus has yet to be addressed. From an epidemiologic standpoint, the means by which BRSV perpetuates in the cattle population has yet to be elucidated. Although progress has been made in understanding the pathogenesis and immune response to BRSV, the mechanism of disease production and immune protection is incomplete. Lastly, efficacy testing of existing vaccines need to continue, as well as the development of new vaccines and new approaches to vaccination.